title: Metabolism of L-methionine linked to the biosynthesis of volatile organic sulfur-containing compounds during the submerged fermentation of Tuber melanosporum.
abstract: Tuber melanosporum, known as the black diamond of cuisine, is highly appreciated for its unique and characteristic aroma, which is mainly due to its volatile organic sulfur-containing compounds (VOSCs). In this work, by adding 5 g/L L-methionine to the fermentation medium, the activities of aminotransferase and α-ketoacid decarboxylase were significantly enhanced by 103 and 250%, respectively, while the activities of alcohol dehydrogenase and demethiolase were decreased by 277 and 39%. Then, the six VOSCs, i.e., methanethiol (MTL), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), 3-(methylthio)propanal (methional), and 3-(methylthio)-1-propanol (methionol), were first detected in the submerged fermentation of T. melanosporum. These results indicated that the biosynthesis of VOSCs was triggered by aminotransferase and α-ketoacid decarboxylase. The production of methional and methionol increased with the increased concentrations of L-methionine (i.e., 5, 10, 15, and 20 g/L) before day 4 of the culture protocol, and methionol was the major product in the Ehrlich pathway. The production of MTL was significantly decreased after day 4 with a significantly increased DMDS, and DMDS was the major product of the demethiolation pathway. Compared with the demethiolation pathway with a total flux of sulfur of 11.33-24.32 μM, the Ehrlich pathway with a total flux of sulfur of 6,149-10,330 μM was considered the major pathway for the biosynthesis of VOSCs. This is the first report linking the metabolism of L-methionine to the biosynthesis of VOSCs by the Ehrlich and demethiolation pathways during the submerged fermentation of T. melanosporum.
authors.affiliation: Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei University of Technology, Wuhan, 430068, China.
authors.forename: Rui-Sang
authors.initials: RS
authors.lastname: Liu
authors.forename: Huan
authors.initials: H
authors.lastname: Zhou
authors.forename: Hong-Mei
authors.initials: HM
authors.lastname: Li
authors.forename: Zhan-Peng
authors.initials: ZP
authors.lastname: Yuan
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.forename: Ya-Jie
authors.initials: YJ
authors.lastname: Tang
mesh_terms: D001203:Ascomycota / Q000737:chemistry / Q000378:metabolism*; D005285:Fermentation; D007218:Industrial Microbiology; D008715:Methionine / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000737:chemistry / Q000378:metabolism*
chemical_list: D055549:Volatile Organic Compounds; D013455:Sulfur; D008715:Methionine